sunflower oil, for greasing
1 1/2 cup
unsalted butter, at room temperature
plums, halved and pitted
packed, dark brown sugar
2 heaping tsp
1/3 cup plus 1 tbsp
- Preheat the oven to 375°F. Grease a 23cm/9-inch round springform cake pan with sunflower oil and place on a baking sheet.
- For the caramel, put 225g/1 cup plus 2 tablespoons of the granulated sugar into a small, wide, heavy pan over low heat. Without stirring, let the sugar dissolve completely. Once liquid, let it gently bubble for 15–20 minutes, until it is a deep golden color. Add 1 tablespoon of the butter, half the vanilla extract and the salt, gently swirling the pan to combine the butter as it melts. Once fully incorporated, immediately remove from the heat and pour the caramel into the prepared cake pan. Place the plum halves on top, cut side down, nestled tightly together, and set aside.
- In a large bowl, beat the remaining 85g/6 tablespoons butter together with the remaining 75g/6 tablespoons granulated sugar and the brown sugar until pale and creamy: this will take 2–3 minutes using electric beaters; if you don’t have them, use a wooden spoon. Add the eggs one at a time, beating well. Once the eggs are well combined, add the remaining vanilla extract, the cornstarch, almond meal, flour and baking powder to the bowl and fold through with a spoon until just combined (taking care not to overmix), then pour over the plums. Smooth the top, then bake for 50–55 minutes until cooked through; a thin skewer inserted in the center should come out clean.
- Transfer the cake to a wire rack and let cool in the pan for 5 minutes. Place a serving plate on top of the pan and flip over before releasing the sides of the pan and removing the base. Let the cake cool for another 5 minutes before slicing.